This invention relates generally to impact or impulse drive type irrigation sprinklers, and more sprinklers which insures that a constant drive force is maintained regardless of nozzle size.
Impulse or impact drive type sprinklers (hereinafter referred to as "impulse type sprinklers") have long been used int he irrigation arts for the watering of crops, lawns, trees, shrubs, and the like. Such sprinklers typically comprise a sprinkler body mounted for rotation on a riser coupled to a suitable source of pressurized water, upwardly and outwardly away from the sprinkler body. The sprinkler body carries a spring biased osciallating drive arm having a drive spoon at one end which effects rotation of the sprinkler body by repeatedly oscillating into and out of the stream from the sprinkler nozzle. As the drive spoon intercepts the stream from the sprinkler nozzle, the stream is deflected laterally creating a torsional force on the drive arm to rotate the spoon out of and away from the stream. The drive spoon is then returned to the stream by an arm spring coupled between the drive arm and the sprinkler body, and upon re-entering the stream, the drive arm impacts against the sprinkler body causing an incremental rotation of the body about the supply riser.
One problem which has long been recognized in the impulse type sprinkler art is that of erratic and non-uniform oscillation of the drive arm caused by the use of various sized sprinkler nozzles. Most impulse type sprinklers typically are designed for use with a variety of nozzle sizes, the nozzles being changeable to permit the user to vary the water application rate and area covered to suit the particular needs. Each different size nozzle, however, produces a different flow and thus imparts a different force to the drive spoon, thereby resulting in variations in the speed of drive arm oscillation and, consequently, the speed of rotation of the sprinkler body.
Various attempts have been made to overcome this problem, typically by altering the geometry of the drive spoon so that only a constant size segment of the stream from any given nozzle is intercepted. Exemplary of such an attempt is that disclosed in U.S. Pat. No. 3,726,479, assigned to the assignee of the present application, and which proposes a specially designed drive spoon having a deflector portion modified so that only a substantially constant size segment of the stream from any given nozzle will be used to drive the sprinkler. While use of specially designed drive spoons such as suggested in the foregoing patent have met with considerable success, the range of nozzle sizes usable has still been limited since oversized nozzles may still impart excessive force to the deflector portion of the spoon.
Another problem raised by the use of various size nozzles with impulse type sprinklers is that of the possibility of reverse rotation of the sprinkler body caused by excessive drive force when a sprinkler nozzle larger than that for which the sprinkler was designed is used. When such an oversized sprinkler nozzle is used, the drive arm may actually be driven out of the stream with such great force as to cause the arm to impact against the sprinkler body in the opposite direction, thereby producing an incremental reverse rotation. One attempt to overcome this problem is disclosed in U.S. Pat. No. 4,055,304, also assigned to the assignee of the present application, and which suggests the use of a secondary arm spring operable when the impact arm rotates in excess of a predetermined arc due to excessive rotational force being applied to the drive spoon.
While each of the foregoing attempts at solving the problems of erratic and uneven sprinkler rotation have met with some degree of success, there still exists a need for device which permits an impulse type sprinkler to be capable of use with a wide variety of nozzle sizes, but which rotates in a constant and predictable manner. As will become more apparent hereinafter, the present invention fulfills that need in a novel and unobvious manner.